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Application Notes

Circuits from the Lab

New Product Briefs

Technical Articles

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Power Management Home

Application Notes

AN-1311: Complex Power Supply Sequencing Made Easy

Power supply sequencing is required for microcontrollers, field programmable gate arrays (FPGAs), digital signal processors (DSPs), analog-to-digital converters (ADCs), and other devices that operate from multiple voltage rails. These applications typically require that the core and analog blocks be powered up before the digital input/output (I/O) rails, although some designs may require other sequences. Proper power-up and power-down sequencing can prevent both immediate damage from latch-up and long-term damage from electrostatic discharge (ESD). In addition, sequencing the supplies staggers the inrush current during power-up, an especially helpful technique in applications operating from current-limited supplies. This Application Note discusses the advantages and disadvantages of using discrete components to sequence the power supplies and describes a simple, yet effective, method of achieving sequencing by using the internal precision enable pins of the ADP5134, which combines two 1.2 A buck regulators with two 300 mA low dropout (LDO) regulators. It also describes sequencer ICs that may be useful for applications that require more accurate and flexible sequencing.

AN-1306: ADP1050 and ADP1051 EEPROM Programming and Calibration in the Power Supply Manufacturing Environment

This 11-page Application Note specifies the EEPROM programming and calibration for the ADP1050 and ADP1051 digital controllers for isolated power supplies during power supply manufacturing. First, the hex file used for EEPROM programming is generated by the GUI software in the power supply development stage. Second, using the generated hex file, the EEPROM can be programmed. Finally, the calibration procedure is presented.

AN-1269: Designing an Inverting Power Supply Using the ADP2441/ADP2442 Synchronous Step-Down DC-to-DC Regulators

Applications such as bipolar amplifiers, optical modules, CCD bias, and OLED displays usually require a negative output voltage from a positive input voltage. Designers of power management systems need versatile switching controllers and regulators that allow them to solve these power management challenges. The ADP2441/ADP2442 switching regulators provide synchronous buck functionality, ranging from a 36 V input voltage down to 0.6 V output voltage at up to 1 A with a switching frequency range from 300 kHz to 1 MHz. Although targeted for synchronous step-down applications, their versatility allows them to realize an inverting buck boost topology, which can generate a negative output voltage from a positive input voltage, without additional cost, component count, or solution size. This Application Note describes how to implement a synchronous inverting buck boost topology to generate negative output voltages from positive input power supplies.

AN-1253: Layout Considerations for Digital Power Management (ADP1046A)

The ADP1046A secondary side digital power controller features analog-to-digital converters, integrated I2C communication, analog comparators, and digital compensation. Layout is crucial for complex mixed signal devices with closely spaced input and output functions, so proper care must be taken to avoid hazards. This 7-page Application Note provides guidelines to avoid noise coupling and techniques for proper grounding.

Circuits from the Lab

CN0280: Robust Completely Isolated Current Sense Circuit with Isolated Power Supply for Solar Photovoltaic Converters

This completely isolated current sensor with isolated power source is highly robust and can be mounted close to the sense resistor for accurate measurements and minimum noise pickup. The 16-MHz output data stream from a sigma-delta modulator is processed by a DSP using a SINC3 digital filter. Ideal for monitoring the ac current in solar photovoltaic (PV) converters, the circuit can handle peak ac voltages of several hundred volts and currents between a few mA and 25 A.

Fully Isolated Lithium Ion Battery Monitoring and Protection System (CN0235)

Lithium ion (Li-Ion) battery stacks contain a large number of individual cells that must be monitored correctly in order to enhance the battery efficiency, prolong the battery life, and ensure safety. The 6-channel AD7280A devices in this circuit act as the primary monitor, providing accurate voltage measurement data to the System Demonstration Platform (SDP-B) evaluation board; the 6-channel AD8280 devices act as the secondary monitor and protection system. Both devices can operate from a single wide supply range of 8 V to 30 V and operate over the industrial temperature range of −40C to +105C. The AD7280A contains an internal 3-ppm reference that allows a cell voltage measurement accuracy of 1.6 mV. The ADC resolution is 12 bits and allows conversion of up to 48 cells within 7 μs. The AD8280 functions independently of the primary monitor and provides alarm functions, indicating out of tolerance conditions. It contains its own reference and LDO, both of which are powered from the battery cell stack. The reference, in conjunction with external resistor dividers, is used to establish overvoltage/undervoltage trip points. Each channel contains programmable deglitching circuitry to avoid alarming from transient input levels. The AD7280A and AD8280, which reside on the high voltage side of the battery management system, have a daisy-chain interface, allowing up to eight AD7280As and eight AD8280s to be stacked together and 48 Li-Ion cell voltages to be monitored. Adjacent AD7280As and AD8280s can communicate directly, passing data up and down the stack without the need for isolation. The master devices on the bottom of the stack use the SPI interface and GPIOs to communicate with the SDP-B evaluation board. High-voltage galvanic isolation is required to protect the low-voltage side of the SDP-B board at this interface. The ADuM1400 and ADuM1401 digital isolators and the ADuM5404 digital isolator with integrated dc-to-dc converter combine to provide the required eleven channels of isolation in a compact, cost effective solution. The ADuM5404 also provides isolated 5 V to the VDRIVE input of the lower AD7280A and the VDD2 supply voltage for the ADuM1400 and ADuM1401 isolators.

New Product Briefs

October 2014

Digital Power Monitor with PMBus interface

adm1294The ADM1293 and ADM1294 high-accuracy integrated digital power monitors use a 12-bit analog-to-digital converter (ADC) to measure current, voltage, and power. The ADC measures the primary input voltage and an auxiliary input voltage, and determines current by measuring the voltage across an external sense resistor. The digital block multiplies the current and primary input voltage to calculate power. The PMBus interface allows a master controller to read data from the device. The master controller combine this information to calculate the current, voltage, power, and energy consumption over time. The devices generate an interrupt signal when an overcurrent, overvoltage, undervoltage, or overpower condition occurs. The ADM1293 is designed for high-side monitoring over a 0-V to 20-V range. The ADM1294 is designed for low-side monitoring. Its integrated shunt regulator allows it to operate over a wide voltage range. Available in 16-lead LFCSP and 14-lead TSSOP packages, the ADM1293/ADM1294 are specified from 40C to +105C and priced from $2.79/$2.99 in 1000s.

September 2014

2-MHz, synchronous boost DC-to-DC Converters

adp1606/07The fixed-output ADP1606 and adjustable-output ADP1607 high-efficiency, fixed-frequency, synchronous, step-up dc-to-dc switching converters provide an output voltage between 1.8 V and 3.3 V for use in portable applications. The 2-MHz operating frequency enables the use of small footprint, low profile external components; and the synchronous rectification, internal compensation, internal fixed current limit, and current mode architecture allow for excellent transient response and a minimal external part count. Other key features include fixed PWM and light load PFM mode options, true output isolation, thermal shutdown (TSD), and logic controlled enable. Operating from as little as 0.9 V, the ADP1606/07 draw 23 A in auto-operating mode and 60 nA in shutdown mode. Available in 6-lead LFCSP packages, they are specified from 40C to +85C and priced at $1.14 in 1000s.

Ultralow-noise (5 V) Linear Regulators have high PSRR, fast transient response

adm717xThe ADM7170, ADM7171, and ADM7172 low dropout linear regulators (LDO) operate from 2.3 V to 6.5 V and provide up to 0.5/1.0/2.0 A output currents, making them ideal for regulation of high-performance analog and mixed-signal circuits operating on 1.2 V to 6 V rails. They provide 60-dB power supply rejection and 5-V output noise independent of output voltage, and achieve excellent line and load transient response with just a small 4.7 μF ceramic output capacitor. Load transient response is typically 1.5 μs for a 1 mA to 500 mA load step. They are available in 17 fixed-output-voltage options from 1.3 V to 5.0 V, and an adjustable version that allows output voltages from 1.2 V to VIN − VDO. Inrush current can be controlled via the soft start pin; the typical start-up time with a 1-nF soft start capacitor is about 1.0 ms. Available in 8-lead LFCSP packages, the ADM7170/71/72 are specified from 40C to +125C and priced at $0.88/$1.19/$1.79 in 1000s.

August 2014

Hot-Swap Controller with PMBus interface monitors energy and power

adm1278The ADM1278 hot-swap controller allows a circuit board to be removed from or inserted into a live backplane. The current-sense amplifier determines the load current by sensing the voltage across a resistor in the power path. The 12-bit ADC measures the load current, supply voltage, output voltage, and temperature at the external NPN device. The PMBus interface allows a controller to read data from the ADC. As many as 16 unique I2C addresses can be selected. The device features overvoltage (OV) and undervoltage (UV) protection, and a PWRGD signal that detects when the output supply is valid. Operating on a 4.5-V to 20-V supply, the ADM1278 draws 5.5 mA. Available in a 32-lead LFCSP package, it is specified from 40C to +85C and priced from $2.89 in 1000s.

Technical Articles

Glenn Morita, LDO Headroom and Its Effects on Output Noise and PSRR, Analog Dialogue, 2014-09-03

Luca Vassalli, Minimum Load Current OperationZero-Load Operation, Analog Dialogue, 2014-09-03

Wenshuai Liao and Luis Orozco, Accurate Analog Controller Optimizes High-Efficiency Li-Ion Battery Manufacturing, Analog Dialogue, 2014-08-06

Aldrick S. Limjoco, Understanding Switching Regulator Output Artifacts Expedites Power Supply Design, Analog Dialogue, 2014-08-06

Jess Espiritu, Complex Power-Supply Sequencing Made Easy, Analog Dialogue, 2014-06-04

Irvin Ou, Simple Circuit Allows Backward Compatibility for Digital Power Controllers, Analog Dialogue, 2014-05-05

David Rice, Dynamic power control minimises power loss, maximises temperature range, EE Times Europe, 2014-04-16

David Rice, Dynamic power control minimises power loss, maximises temperature range, EDN Europe, 2014-04-16

Frederik Dostal, Digital power management without code qualification, Power Systems Design, 2014-03-03

Glenn Morita, Noise-Reduction Network for Adjustable-Output Low-Dropout Regulators, Analog Dialogue, 2014-03-03

Maurice O'Brien, Integrated Power Management Unit Simplifies FPGA-Based System, Electronics Maker, 2013-12-28

Maurice O'Brien, Highest Power Density, Multi-Rail Power Solution For Space-Constrained Applications, Analog Dialogue, 2013-11-01

Frederik Dostal, Power Management for Health Care Applications, Power Systems Design, 2013-10-17

Webinars and Tutorials

Galvanic Isolation for Power Supply Applications -- This seminar discusses isolation and isolation technologies in terms of signal transmission methods and isolation materials, including optocouplers and digital isolators. Ii covers isolation usage, including current sensing, gate driver, and communication functions in ac-to-dc, motor control, hybrid electrical vehicles, PV, and other power supply applications.

Solving Isolation Challenges in Power Conversion Applications - This webcast will present solutions to isolation challenges in power conversion applications. Among the topics to be discussed are the limitations of traditional methods of isolation (such as utilization of optocouplers and pulse transformers) vs. more efficient and cost effective solutions that utilize digital isolators. If you are currently using optocouplers and pulse transformers, this is a webcast you should attend.

Design Techniques for reducing power consumption and harmful thermal events in industrial designs - This webcast will present: typical analog module configuration and how to calculate the maximum ambient temperature that the system can tolerate, new technology to reduce the power dissipated in the module (regardless of what output load is connected), and the performance of these devices when the supply is run from a switching regulator rather than with a linear regulator.

Fundamentals of Designing with Semiconductors: Powering Your Circuit - What is important about a power supply and how does it work? What different types of power supplies and conversion methods are used? How can a power supply affect the signal chain and how do you select the best regulator for your circuit? This webcast will also explain noise, ripple, line and load regulation, power supply rejection ratio, the effects of temperature change, and other specifications that impact power supply performance.


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